The present invention relates to a method for increasing filler retention of cellulosic fiber sheets and, more particularly, to a method for increasing filler retention for cellulosic fiber sheets by incorporating cellulosic fibers having increased anionic sites into the sheet.
Fillers are often incorporated into cellulosic fiber sheets to provide paper products having enhanced printability and improved optical properties. However, the improvement provided by filler is limited by the amount of filler that can be retained by the fiber sheet. Accordingly, there exist a need for methods for increasing fiber capacity for filler and for increasing the filler retention of fiber sheets. The present invention seeks to fulfill these needs and provides further related advantages.
In one aspect, the present invention provides a method for increasing filler retention of cellulosic fiber sheets. In the method, cellulosic fibers with increased anionic sites are treated with either positively charged and/or amphoteric filler particles or a cationic retention aid and negatively charged and/or amphoteric filler particles to provide sheets having increased filler retention.
In another aspect of the invention, cellulosic fiber sheets with retained filler particles are provided. In one embodiment, fiber sheets with retained positively charged and/or amphoteric filler particles are provided and, in another embodiment, the fiber sheets with retained negatively charged and/or amphoteric filler particles are provided.
In a further aspect, a method for increasing drainage from a papermaking furnish is provided. In the method, cellulosic fibers having increased anionic sites are incorporated into the furnish.